It will be possible to upgrade machines running XP and Vista to Windows 8. But it could wipe out all of your Windows apps, reports Mary Jo Foley on CNET.

Microsoft has really only promised that Windows 7 users will be able to easily use Windows 8. Windows 7 apps, files, and most system tweaks and settings will be preserved after Windows 8 is installed.

That won't be true with older versions of Windows, Foley reports. In some cases only your files will be saved.

On top of that, it won't be easy to reinstall your really old Vista or Windows XP apps onto Windows 8. Windows 8 does include something called Hyper-V virtualization—which is a way to run two or more different operating systems on the same PC. In Windows 7, Microsoft had a different kind of virtualization built it. That was something called XP Mode. This included a copy of XP and let you run an XP app in a Window side by side with Windows 7 apps.

But Microsoft killed that feature in Windows 8, according to Windows guru Paul Thurrott on the Supersite for Windows. So even if you could find a copy of XP and get it loaded and then reinstall your XP apps, switching between them won't be as smooth.

Microsoft doesn't want you to keep using your old Windows apps. It wants you to move on already and buy new software designed for its Metro interface. That's one of the reasons that enterprises won't be interested in adopting Windows 8 for a long time.

If all that wasn't enough to discourage you from buying Microsoft's fancy new operating system for your older-but-perfectly-fine PC, think about this: Windows 8 is really designed for a touchscreen. Reviewers say that using Windows 8 with a mouse is confusing and clunky.

If you buy a new PC between now and whenever Windows 8 arrives for consumers (supposed to be this fall), you can get an upgrade to Windows 8 Pro for $15. But here's a thought. If you want Windows 8, just wait until the new touch PCs get here.